Vibrational dephasing in liquid nitrogen at high densities studied with time-resolved stimulated Raman gain spectroscopy

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Abstract
In highly compressed liquid nitrogen at 295 K we observe a sharp increase in the vibrational dephasing rate T−12 with increasing density, indicating that at high fluid densities (2.3 to 2.9×1022 cm−3) the modulation of the vibrational frequency shows a stronger density dependence than the bath correlation time due to the action of short range repulsive forces. The observed behavior shows good agreement with results of previously published molecular dynamics simulations and a fit to a binary interaction model. When the phase transition from the liquid to the solid state takes place we observe a sudden drop in T–12 by a factor of 4. We also present the variation of the Raman line shift of liquid and solid nitrogen with pressure over a region of 0.5 to 4.6 GPa at 295 K.